<template>
  <div>
    <div class="shopcart">
      <div class="content" @click="toggleList">
        <div class="content-left">
          <div class="logo-wrapper">
            <div class="logo" :class="{'highlight':totalPrice>0}">
              <i class="icon-shopping_cart" :class="{'highlight':totalPrice>0}"></i>
            </div>
            <div class="num" v-show="totalCount>0">{{totalCount}}</div>
          </div>
          <div class="price">¥{{totalPrice}}</div>
          <div class="desc">另需配送费{{deliveryPrice}}元</div>
        </div>
        <div class="content-right" @click.stop.prevent="pay">
          <div class="pay" :class="payClass">{{payDesc}}</div>
        </div>
      </div>
      <div class="ball-container" v-for="ball in balls">
        <transition name="drop" v-on:before-enter="beforeEnter" v-on:enter="enter"  v-on:after-enter="afterEnter">
          <div class="ball" v-show="ball.show">
            <div class="inner inner-hook"></div>
          </div>
        </transition>
      </div>
      <!--购物车列表-->
      <transition name="fold">
        <div class="shopcart-list" v-show="listShow">
          <div class="list-header">
            <h1 class="title">购物车</h1>
            <span class="empty" @click="empty">清空</span>
          </div>
          <div class="list-content" ref="listContent">
            <ul>
              <li class="food" v-for="food in selectFoods" v-show="food.count">
                <span class="name">{{food.name}}</span>
                <div class="price">
                  <span>¥{{food.price * food.count}}</span>
                </div>
                <div class="cartcontrol-wrapper">
                  <cartcontrol :food="food" @cartAdd="drop"></cartcontrol>
                </div>
              </li>
            </ul>
          </div>
        </div>
      </transition>
    </div>
    <transition name="fade">
      <div class="list-mask" v-show="listShow" @click="hideList"></div>
    </transition>
  </div>
</template>

<script type="text/ecmascript-6">
  import BScroll from 'better-scroll';
  import cartcontrol from 'components/cartcontrol/cartcontrol';

  export default{
    data() {
      return {
        balls: [
          {show: false},
          {show: false},
          {show: false},
          {show: false},
          {show: false}
        ],
        dropBalls: [],  // 正在执行动画的小球.
        fold: true
      };
    },
    props: {
      selectFoods: {
        type: Array,
        default() {  // 在props里面,如果定义的属性为Array或Object则default要定义成函数.
          return [];
        }
      },
      deliveryPrice: {
        type: Number,
        default: 0
      },
      minPrice: {
        type: Number,
        default: 0
      }
    },
    computed: {
      totalPrice() {
        let total = 0;
        this.selectFoods.forEach((food) => {
          total += food.price * food.count;
        });
        return total;
      },
      totalCount() {
        let count = 0;
        this.selectFoods.forEach((food) => {
          count += food.count;
        });
        return count;
      },
      payDesc() {
        if (this.totalPrice === 0) {
          return `¥${this.minPrice}起送`;
        } else if (this.totalPrice < this.minPrice) {
          let diff = this.minPrice - this.totalPrice;
          return `还差¥${diff}起送`;
        } else {
          return '去结算';
        }
      },
      payClass() {
        if (this.totalPrice < this.minPrice) {
          return 'not-enough';
        } else {
          return 'enough';
        }
      },
      listShow() {
        if (!this.totalCount) {
          this.fold = true;
          return false;
        }
        let show = !this.fold;
        if (show) {
          this.$nextTick(() => {
            if (!this.scroll) {
              this.scroll = new BScroll(this.$refs.listContent, {
                click: true
              });
            } else {
              this.scroll.refresh();
            }
          });
        }
        return show;
      }
    },
    methods: {
      drop(el) {
        // 每次都拿一个show为false的球进行动画，这里有5个，足够用的了。除非5个球全都在执行动画。
        for (let i = 0; i < this.balls.length; i++) {
          let ball = this.balls[i];
          if (!ball.show) {
            ball.show = true;
            ball.el = el;
            this.dropBalls.push(ball);
            return;
          }
        }
      },
      beforeEnter(el) {
        let count = this.balls.length;
        while (count--) {
          let ball = this.balls[count];
          if (ball.show) {
            // 获取该元素相对于视口的位置，返回的rect的left和top就是它相对于这个视口的偏移。
            let rect = ball.el.getBoundingClientRect();
            // 下面的x,y是购物车上的小球相对于自身原来位置在水平方向和垂直方向上的偏移。
            // x是向右偏移，故是正的，y由于是向上偏移，所以是负值。
            let x = rect.left - 32;
            let y = -(window.innerHeight - rect.top - 22);
            el.style.display = '';    // v-show会将元素的display置位none，故此处手动将其显现出来。
            // el负责y轴方向上平移，inner负责x轴方向上平移.
            el.style.webkitTransform = `translate3d(0, ${y}px, 0)`;
            el.style.transform = `translate3d(0, ${y}px, 0)`;
            let inner = el.getElementsByClassName('inner-hook')[0];
            inner.style.webkitTransform = `translate3d(${x}px, 0, 0)`;
            inner.style.transform = `translate3d(${x}px, 0, 0)`;
          }
        }
      },
      enter(el, done) {
        // 手动触发浏览器重绘
        let refresh = el.offsetHeight;
        this.$nextTick(() => {
          el.style.webkitTransform = 'translate3d(0, 0, 0)';
          el.style.transform = 'translate3d(0, 0, 0)';
          let inner = el.getElementsByClassName('inner-hook')[0];
          inner.style.webkitTransform = 'translate3d(0, 0, 0)';
          inner.style.transform = 'translate3d(0, 0, 0)';
          // 实际效果发现下面这行代码也可以不要
          el.addEventListener('transitionend', done);
        });
      },
      afterEnter(el) {
        let ball = this.dropBalls.shift();
        if (ball) {
          ball.show = false;
          el.style.display = 'none';
        }
      },
      toggleList() {
        if (!this.totalCount) {
          return; // 表示不响应点击事件
        }
        this.fold = !this.fold;
      },
      empty() {
        this.selectFoods.forEach((food) => {
          // 这里没必要将整个数组清空,清空其count属性即可.当然清空数组也是可以的,不过务必倒着遍历删除,否则会有遗漏.
          // 为什么遍历selectFoods将它每个元素的count属性置为0可以呢?
          // 因为shopcart组件作为父组件引用了cartcontrol组件, 引用的同时给它绑定了food对象,
          // cartcontrol组件中food.count发生变化,是会引起界面重新渲染的(v-show="food.count>0").
          food.count = 0;
        });
      },
      hideList() {
        this.fold = true;
      },
      pay() {
        if (this.totalPrice < this.minPrice) {
          return;
        }
        window.alert(`需要支付${this.totalPrice}元`);
      }
    },
    components: {
      cartcontrol
    }
  };
</script>

<style lang="stylus" rel="stylesheet/stylus">
  @import "../../common/stylus/mixin.styl"

  .shopcart
    position: fixed
    left: 0
    bottom: 0
    z-index: 50
    width: 100%
    height: 48px
    .content
      display: flex
      background: #141d27
      font-size: 0
      color: rgba(255, 255, 255, 0.4)
      .content-left
        flex: 1
        .logo-wrapper
          display: inline-block
          vertical-align: top
          position: relative
          top: -10px
          margin: 0 12px
          padding: 6px
          width: 56px
          height: 56px
          box-sizing: border-box
          border-radius: 50%
          background: #141d27
          .logo
            width: 100%
            height: 100%
            border-radius: 50%
            text-align: center
            background: #2b343c
            &.highlight
              background: rgb(0, 160, 220)
            .icon-shopping_cart
              line-height: 44px
              font-size: 24px
              color: #80858a
              &.highlight
                color: #fff
          .num
            position: absolute
            top: 0
            right: 0
            width: 24px
            height: 16px
            line-height: 16px
            text-align: center
            border-radius: 16px
            font-size: 9px
            font-weight: 700
            color: #fff
            background: rgb(240, 20, 20);
            box-shadow: 0, 4, 8, 0, rgba(0, 0, 0, 0.4)
        .price
          display: inline-block
          vertical-align: top
          margin-top: 12px
          line-height: 24px
          padding-right: 12px
          box-sizing: border-box
          border-right: 1px solid rgba(255, 255, 255, 0.1)
          font-size: 16px
          font-weight: 700

        .desc
          display: inline-block
          vertical-align: top
          margin: 12px 0 0 12px
          line-height: 24px
          font-size: 10px
      .content-right
        flex: 0 0 105px
        width: 105px
        .pay
          height: 48px
          line-height: 48px
          text-align: center
          font-size: 12px
          font-weight: 700
          background: #2b333b
          &.not-enough
            background: #2b333b
          &.enough
            background: #00b43c
            color: #fff

    .ball-container
      .ball
        position:fixed
        left:32px
        bottom: 22px
        z-index: 200
        transition: all 0.4s cubic-bezier(0.49,-0.29,0.75,0.41)
        .inner
          width:16px
          height:16px
          border-radius:50%
          background: rgb(0,160,220)
          transition: all 0.4s linear
    .shopcart-list
      position: absolute
      left: 0
      top: 0
      z-index: -1
      width: 100%
      opacity: 1
      transform: translate3d(0, -100%, 0)
      &.fold-enter-active, &.fold-leave-active
        transition: all 0.5s linear
      &.fold-enter, &.fold-leave-to
        opacity: 0
        transform: translate3d(0, 0, 0)
      &.fold-enter-to, &.fold-leave
        opacity: 1
        transform: translate3d(0, -100%, 0)
      .list-header
        height: 40px
        line-height: 40px
        padding: 0 18px
        background: #f3f5f7
        border-bottom: 1px solid rgba(7, 17, 27, 0.1)
        .title
          float: left
          font-size: 14px
          color: rgb(7, 17, 27)
        .empty
          float: right
          font-size: 12px
          color: rgb(0, 160, 220)
      .list-content
        padding: 0 18px
        max-height: 217px
        overflow: hidden
        background: #fff
        .food
          position: relative
          padding: 12px 0
          box-sizing: border-box
          border-1px(rgba(7, 17, 27, 0.1))
          .name
            line-height: 24px
            font-size: 14px
            color: rgb(7, 17, 27)
          .price
            position: absolute
            right: 90px
            bottom: 12px
            line-height: 24px
            font-size: 14px
            font-weight: 700
            color: rgb(240, 20, 20)
          .cartcontrol-wrapper
            position: absolute
            right: 0
            bottom: 6px

  .fade-enter-active, .fade-leave-active
    transition: all 0.5s linear

  .fade-enter, .fade-leave-active
    opacity: 0
    background: rgba(7, 17, 27, 0)

  .list-mask
    position: fixed
    top: 0
    left: 0
    width: 100%
    height: 100%
    z-index: 40
    background: rgba(7, 17, 27, 0.6)
    backdrop-filter: blur(10px)
</style>
